Transfer of impulsive loading on cladding panels to the fixing assemblies

The fixing assemblies for prefabricated cladding panels on buildings, are often designed on an empirical basis, to support the dead weight of the panel, wind loads and possibly temporary loads arising during construction. If, subsequently, the design loads are accidentally exceeded but the panel is undamaged; it may be necessary to check the condition of the fixings. A physical check would require costly dismantling and reconstruction of the panel but, as an alternative, this paper presents an analysis of the force transferred to cladding fixing assemblies when the panel is subjected to impulsive loading, using the finite element analysis program, DYNA3D. The results were validated with experimental results from impact tests on a steel plate supported on four steel bars. Having obtained this validation, a finite element analysis was then carried out to determine the response of fixings for panels under different levels of blast loading using two different models for the panel-fixing assemblies. The first model considers only the effect of out-of-plane fixing, whilst in the second model both the out-of-plane fixings and in-plane fixings are considered. It was observed that forces transferred to fixings include an axial force, shear forces, and bending moments and these force components can vary along the length of the fixing. Inspections of cladding panels, after being subjected to impulsive loads, often show that the connection between the fixing and the panel and between the fixing and the support structure are more vulnerable to impulsive loading than the panel itself. The FE analysis has shown that forces in the fixings are related to the dynamic response of the cladding panel; hence damage to the fixings could be deduced from damage to the panel.